Conventionally, there have been measured circuit parameters (such as the S parameters) of a device under test (DUT) (refer to a patent document 1 (Japanese Laid-Open Patent Publication (Kokai) No. H11-38054, for example). A description will now be given of a measurement method of the circuit parameters of a device under test (DUT) according to the prior art with reference to FIG. 16.
A signal is transmitted from a signal source 130 to a reception unit 140 via a DUT 400. The signal is received by the reception unit 140. It is possible to acquire the S parameters and frequency characteristics of the DUT 400 by measuring the signal received by the reception unit 140.
On this occasion, measurement system errors are generated in the measurement due to mismatching between a measurement system such as the signal source 130 and the DUT 400, and the like. This measurement system errors include Ed: error caused by the direction of a bridge, Er: error caused by frequency tracking, and Es: error caused by source matching, for example. FIG. 17 shows a signal flow graph relating to the signal source 130. RF IN denotes a signal input from the signal source 130 to the DUT 400 and the like, S11m denotes an S parameter of the DUT 400 and the like acquired based upon a signal reflected from the DUT 400 and the like, and S11a denotes a true S parameter of the DUT 400 and the like without the measurement system errors.
On this occasion, it is possible to correct the errors according to the patent document 1, for example. The correction in this way is referred to as calibration. A brief description will now be given of the calibration. A calibration kit is connected to the signal source 130 to realize three types of states: open-circuit, short-circuit, and load (standard load Z0). In these states, a signal reflected from the calibration kit is acquired by a bridge to obtain three types of the S parameter (S11m) corresponding to the three types of states. The three types of variables Ed, Er, and Es are obtained from the three types of S parameter.
However, according to the above prior art, it is necessary to attach/detach three types of calibration kits: open-circuit, short-circuit, and load (standard load Z0), to/from the signal source 130. The number of operations of attachment/detachment is twice (attachment and detachment) for the one type of the calibration kit. As a result, the number of the operations to attach/detach the three types of the calibration kits is six. Upon the calibration, there poses a problem that the number of the attachments and detachments of the calibration kits increases, resulting in complicated operations.
In view of the foregoing problem, an object of the present invention is to calibrate the measurement system used for the circuit parameters of a device under test with a reduced number of the attachments/detachments of the calibration kits.